Silencer for internal combustion engines



Dec. 8, 1936. e. BACCHETTl-RIGHETTI 2,063,270

SILENCER FOR INTERNAL COMBUSTION ENGINES Filed Sept. 18, 1935 Q Patented Dec. 8, 1936 SILENCEB FOB. mama oosmv's'rioiv J moms Giorgio Bacchetti-ltighetti, Rome, Italy Application September 18, 1935, Serial No. 41,154

' In Italy June 3, 1935 1 Claim.

Subject matter of this invention is a silencer for internal combustion engines the fundamental feature of which consists in imparting, by helical surfaces and ducts, to the exhaust gases an intermittently inverted rotary movement so as to produce a dynamic resistance to the flow ofsaid gases which, though being quite free in their propulsive expansion movement, are guided by the spiral way and discharged from the exhaust with diminished velocity and detonation. I

With my improved silencer, to the increase of number of revolutions of the engine corresponds an increase of silencing without ible increase of losses of efllciency of engine being caused by silencer.

One of the objects of my present invention consists in providing a silencer which besides having a high efllciency increasing with the number of revolutions of engine, permits of a minimum counterpressure to exhaust as compared with usual silencers of equal efilciency.

In the structure of silencer the volume, the number of helices and the pitch vary according to the efiiciency and number, of cylinders of the as engine with which it is to be used.

The invention is shown by way of an illusti'ative, not limitative, example in the annexed drawing, in which:

- Fig. 1 is a longitudinal section of the silencer so subject matter of invention, with parts in elevation, and

Fig. 2 is a section on line 11-11 of Pig. 1.

with reference to this drawing, in, a case or housing i having an admission aperture 2 and a as discharge aperture 3 for the exhaust gases there is arranged, in perfect contact with the casing, a series of sections of helical surfaces or vanes l, I, 6, l of alternately opposite pitch so that the gases admittedto opening I are compelledtofirst' 40 pass through a way, for instance left-handed, betweenhelixlandthewallofcasingiuptosection I, and then a right-handed thread way between helix I and wall of easing I up to section Ugand so forth, another left-handed. thread way as up to section IO and a right-handed one up to section ll.

In the reversing sections IJ, II the gases moved with great velocity in a given rotatory n are compelled to suddenly reverse rotation th 50 diiilculty which is the greater the higher is the velocity of the gases. Thereby a pozitive dynamic resistance to the movementof'the iluid, i. e. exnaust gases, is created so that the latter, at last,

are discharged from orifice l with substantially uniform and silent flow.

For further improving the effect of the silencer it may be advantageous to place in front of sec-' tion ii, i. e. between the last helix 1 and the 5 exhaust I, a.disk I! with helical blades (see also Fig. 2) with a turn opposite to that of helix I. In this case the gases leaving the helix 1 still receive a lastchange of rotary direction before reaching exhaust 3. 10

As appears from the drawing, the helices 4, I, 8, and 1 are supported on an axial shaft which, however, may also be omitted. Preferably the first turn it of helix 4 is welded to casing i so as to prevent axial shifting of the group=of helices 15 in casing I. Other known means may be used for fixing helices-l, I, l, and l.

As appears from the drawing which, however.

. is not limitative, helix 4 is of a greater axial length than the subsequent helix 5, andsohelix 20 to helix 8, and helix t to helix I. The subsequent helices may also be of different pitch, diameter and length. Particularly, they may be substituted with helically wound tube sections consecutively welded together with alternately right and left-handed thread.

As' is seen from Fig. l, the radial section II of aspire of helix 4 is preferably concave, with the concavity turned tothe entering gases in order to offer a sufiicient mechanical resistance for preventing deformation under pressure of the hot exhaust gases.

My present invention is here described and shown in a preferred modification in a purely illustrative, not limitative way, and any useful or necessary structural alterations'may be applied thereto within the scope of the invention.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, 140 declare that what I claim is:

A silencer for internal combustion engines comprisinga casing having an inlet and an outlet, a shaft extending longitudinally through said casing, a plurality of sections of helical vanes disposed along said shaft, the pitch of alternate sections being in opposite directions, so that a change of direction of rotationis imparted to the exhaust-gases from one section to the other, and the longitudinal extent of each section being successively smaller than that of the preceding section in the direction of the outlet.

GIORGIO BACCHI'I'I'I-RIGHIITI. 

